Variable configuration combustion apparatus

ABSTRACT

A combustion apparatus of a high energy release rate type includes a liner with variable primary and secondary air entrances. The primary air entrance may be adjusted to vary the amount of swirl of the primary air while retaining substantially constant flow area. The secondary air entrance is variable both in area and in location axially of the combustion liner.

O United States Patent 11 1 1111 3,869,246 Hammond, Jr. et al. 1 Mar. 4, 1975 VARIABLE CONFIGURATHON 3,544,246 12/1970 Meyer 431/188 COMBUSTION APPARATUS [75] Inventors: Dean C. Hammond, Jr., Warren; Primar y E.\ammer--Carroll B. Dorlty, Jr. $35 Mafia Detrolt both of Attorney, Agent, or F irmPaul Fitzpatrick [73] Assignee: General Motors Corporation,

Detroit, Mich. 122 Filed: Dec. 26, 1973 [57] ABSTRACT [21] Appl' 428430 A combustion apparatus of a high energy release rate type includes a liner with variable primary and secon- [52] U.S. Cl. 431/351, 431/184 y air entrances. The primary air entrance may be [51] Int. Cl. F23d 15/00 adjusted to ry h mount of swirl of the primary air [58] Field of Search 431/183, 184, 185, 183', while retaining substantially constant flow area. The 431/351, 352 secondary air entrance is variable both in area and in location axially of the combustion liner. [56] References Cited UNITED STATES PA EN S 3 Claims, 5 Drawing Figures 1,781,236 11/1930 Lilge 431/352 PATENTED 4 5 VARIABLE CONFIGURATION COMBUSTION APPARATUS Our invention is directed to combustion apparatus of a high energy release rate type; that is, combustion apparatus which operates under pressure and which is relatively compact for the amount of heat generated. Typically, such combustion apparatus is used in gas turbine engines, although there are other applications.

Our invention is concerned with the provision of variable configuration of the apparatus so as to vary the airflow in such way as to promote complete combustion at various levels of operation, and to minimize the output of substances which may be regarded as atmospheric pollutants.

With this in mind, our combustion apparatus incorporates various features. One of these is means for varying the swirl of primary air; that is, the air intended for combination with the fuel. Another feature is an arrangement for varying both the area and location of secondary air ports, which are those which admit air which dilutes and cools the combustion products and may to some extent serve to complete the combustion of partially burned fuel.

The principal objects of our invention are to provide a combustion apparatus the configuration of which is variable to secure most efficient and clean combustion over a wide operating range; to provide a combustion apparatus with means for varying both the location and effective area of secondary air entrances; and, in general, to provide a combustion apparatus suited to the requirements of gas turbine engines.

The nature of our invention and its advantages will be apparent to those skilled in the art from the succeeding detailed description of the preferred embodiment of the invention and the accompanying drawings.

FIG. 1 is a longitudinal sectional view of a combustion apparatus taken in a plane containing the axis of the combustion liner, with certain accessory apparatus omitted.

FIG. 2 is a cross section of the same, taken in the plane indicated by the line 2-2 in FIG. 1.

FIG. 3 is a detail sectional view taken on the plane indicated by the line 3-3 in FIG. 1.

FIG. 4 is a cross sectional view taken on the plane indicated by the line 4-4 in FIG. 1.

FIG. 5 is a partial longitudinal sectional view taken on the plane indicated by the line 5-5 in FIG. 2.

Referring to the drawings, the combustion apparatus includes a casing 2 and a combustion liner 3 mounted within the casing. The casing includes a side wall 4. A flange 6 welded to the side wall provides for mounting of end wall or cover 7 which includes a front disk 8, a cylindrical wall 10, and a peripheral bolting flange 11, the latter being fixed by bolts (not shown) to the flange 6. The apparatus includes a viewing window 14. A pipe provides an air inlet to the casing from a suitable source such as a compressor.

The liner 3 includes a side wall 16 which is illustrated as cylindrical and of circular cross section, as is preferred. The downstream end of the liner 3 is received between outer and inner flanges 18 and 19 projecting forwardly from a ring 20 on which both are mounted. The ring 20 is bolted to a flange 22 extending inwardly from the casing wall 4. Inner flange I9 defines an outlet 23 for combustion products at the downstream end of liner 3.

The forward or upstream end of liner wall 16 is welded to a flange 24 which is connected through the primary air entrance means 26 to a liner front wall 27. A boss 28 extending from the wall 27 defines a shoulcler which abuts the casing front disk 8 and includes a reduced diameter threaded portion 30 which receives a nut 31 effective tofix the upstream end of the combustion liner in place in relation to the front disk 8. Thermal expansion of the liner is accommodated by any required sliding motion of the downstream end between flanges 18 and 19. A fuel nozzle 32 is threaded into the interior of boss 28 and retained by a nut 34. An igniter 35 fixed to the front disk 8 extends through an opening in the liner front wall 27.

Before proceeding further with a detailed description of the liner and its variable configuration features, it may be pointed out that the casing structure shown is of a test cell type rather than that for an actual gas turbine engine; however, this is immaterial to the operation of the combustion apparatus, and any suitable casing or arrangement of the liner within a gas turbine structure may be employed as desired.

Considering now the structure of the primary air entrance means, this comprises four fixed guides 36 spaced 90 apart around the axis of the liner and welded or otherwise fixed to the liner front wall 27. A threaded boss extends from each fixed guide through an opening in flange 24, and the assembly of front wall.

and fixed guides is held at the upstream end of the liner by four nuts 38. The air entrance also includes four movable guides 39 each fixed by two cap screws 40 to a unison ring 42 rotatable about the axis of the liner. Ring 42 is rotatably mounted on the circular periphery of the liner front wall 27 and is retained by a ring 43 fixed to the front wall by four studs 44 and nuts. It will be noted that the fixed guides 36 diverge in the direction toward the axis whereas the movable guides 39 coilverge in the direction toward the axis. These guides define between them four substantially radial air inlet passages 46 and four somewhat tangential inlet passages 47 alternating with the passages 46.

Air entering passages 47 tends. to swirl around the axis of the liner along the wall of the liner whereas air admitted through the passages 46 tends to penetrate directly toward the fuel nozzle32. There is, of course, some mixing of the two streams in the upstream portion of the combustion liner. Rotation of the unison ring 43 causes enlargement of one set of passages with accompanying contraction of the other set, so that the swirling passages may be either enlarged or reduced with corresponding reduction or enlargement in the radial passages. This change, however, does not significantly affect the total primary air entrance area or the amount of primary air introduced under otherwise constant conditions. The relative amount of primary air is affected by variation of the secondary air entrance means.

The unison ring 42 is rotated to adjust the primary air entrance by a reciprocable rod 48 which extends through a guide 50 to the exterior of wall 10. Guide 50 may include suitable means to minimize leakage of compressed air along the rod 48. The rod terminates in a clevis fitting 51 which is coupled by a bolt 52 to an arm 54 welded to and extending radially from the ring 42. Specifically, the bolt 52 is received in a radial slot 55 in the arm 54. It will be readily apparent how the primary air inlet is varied as the rod 48 is moved either to right or left as illustrated in FIG. 4 to move the arm 54 between the position indicated in broken lines in FIG. 4 and a similar limit position clockwise from the solid line position illustrated in FIG. 4.

Considering now the secondary air entrance means 56, air may enter the liner through six ports 58 elongated axially of the liner. These ports are located approximately midway between the primary air entrance and the combustion products outlet. Each port is defined by a slot in the liner wall 16 and a thin sheet metal spout 59 which fills the slot and projects very slightly into the interior of the liner. This tends to improve penetration of the secondary air and minimize interference between the secondary air and any primary air which may be flowing along the interior of the liner wall.

The arrangement for varying the configuration of the secondary air entrance involves two sleeves 60 and 62. The sleeves are split longitudinally as indicated at 63 so that they will not bind as a result of relative expansion of the liner wall 16 and the sleeves. Each sleeve has internal circumferential ridges near its upstream and downstream edges for better sliding contact with the liner wall. The sleeves are connected to a mechanism for reciprocating them shown principally in FIG. 5. Sleeve 60 has two arms 66 extending from it at 180 spaced positions, and sleeve 62 has similar arms 67 extending from it, these arms being welded to the sleeves. Arms 66 and 67 bear nuts which cooperate with two actuating rods 68 which extend into the combustion apparatus from forward of front disk 8. Each rod 68 is rotatably and reciprocably mounted in a guide 70 welded to the front disk 8 and which may include means for minimizing any leakage of compressed air along the actuating rod 68. A pinion 71 is fixed in any suitable manner to the outer end of each actuating rod 68. These pinions, which have the same number of teeth, mesh with an operating gear 72 having a hub 74. Brazed or otherwise fixed to the faces of the rim of gear 72 are flanges 75 which may bear against the faces of pinions 71 so that the actuating rods 68 may be reciprocated by any suitable actuator reciprocating the hub 74 of gear 72. By rotating gear 72, the rods 68 are rotated concurrently. Gear 72 may be mounted on any suitable support for axial and rotational movement and be reciprocated or rotated by any suitable actuating mechanism or, for that matter, may be adjusted manually.

Each actuating rod 68 is coupled to the sleeves 60 and 62 respectively by a larger diameter threaded portion 76 and a smaller diameter threaded portion 78. These threaded portions are coupled to the arms 66 and 67 by nuts 79 and 80, respectively. These nuts are brazed or otherwise fixed to plates 82 secured to the arms 66 and 67 by cap screws 83. The threads 76 and 78 are of opposite hand, so that rotating the actuating rod causes the sleeves 60 and 62 to go toward or away from each other to vary the width of the gap between them and thus the effective area of secondary air entrance ports 58. When the gear 72 is moved axially, this movement is transmitted through rod 68 to both sleeves which thus may be translated to vary the effective position of the secondary air entrance axially of the liner.

The guides 50 and 70 are not described in detail, since they are commercially available structures of the type used for mounting thermocouples in pressurized gas ducts and for other such purposes. Any suitable guiding and sealing means may be employed in accor dance with our invention.

Referring to the means for introducing fuel, the fuel nozzle 32 is threaded into the boss 28 and retained by nut 34. The body of the fuel nozzle 32 defines an internal passage 84 to which a fuel line may be connected at the threaded portion 86. The details of the fuel nozzle may be such as are most suited for the particular fuel employed. The fuel nozzle specifically illustrated in the drawings is intended to atomize the liquid fuel by discharging it through an annular row of fine orifice jets 87 which direct the fuel radially outward toward the air entering through the primary air entrance 26.

It may be noted that the structure of liner wall 16 is such as to accommodate the addition of a ceramic interior coating or cast ceramic liner. If desired, such a liner could be retained between the guides of the primary air entrance and the flange l9, and might be in segments divided by joints extending circumferentially of the liner.

It will be seen that the combustion apparatus as illustrated is a quite flexible one. The fractions of air flow passing through the various openings; that is, primary and secondary air, can be continuously varied by adjusting the secondary hole area. The flame stabilization characteristics can be varied by varying the portions of primary air entered with swirl and without swirl. The point of reaction quenching of the combustion can be changed by moving the axial location of the secondary air entrance ports. All of these conditions can be varied independently.

These facts make the combustion apparatus as illustrated very suitable for research into optimum combustion chamber geometry and, with the addition of mechanization for adjusting the variable geometry feature, it may readily be incorporated into a working gas turbine engine as the combustion apparatus for such an engine to minimize undesirable products of combustion.

To avoid possible mixunderstanding, we point out that the variable primary air entrance means disclosed herein is derived from the literature.

The detailed description of the preferred embodiment of the invention for the purpose of explaining the principles thereof is not to be considered as limiting or restricting the invention, since many modifications may be made by the exercise of skill in the art.

We claim:

1. A combustion apparatus comprising a casing having an air inlet, a combustion liner of generally cylindrical configuration mounted in the casing, the liner having an upstream end and having a downstream end communicating with an outlet for combustion products, the liner defining primary air entrance means adjacent to the upstream end and secondary air entrance means intermediate the ends; and means adjacent to the upstream end for distributing fuel into the primary air; the said apparatus being characterized by variable configuration secondary air entrance means comprising a ring of ports through the liner; two valve sleeves reciprocable lengthwise of the liner, one sleeve being effective to obstruct variably the upstream ends of the ports and the other sleeve being effective to obstruct variably the downstream ends of the ports; and means for reciprocating the sleeves concurrently in the same direction to vary the effective location of the secondary air entrance means and for reciprocating the sleeves concurrently in opposite directions to vary the effective area of the secondary air entrance means.

2. A combustion apparatus comprising a casing having an air inlet; a combustion liner of generally cylindrical configuration mounted in the casing, the liner having an upstream end and having a downstream end communicating with an outlet for combustion products, the liner defining primary air entrance means adjacent to the upstream end and secondary air entrance means intermediate the ends; and means adjacent to the upstream end for distributing fuel into the primary air; the said apparatus being characterized by variable configuration secondary air entrance means comprising a ring of ports through the liner; two valve sleeves reciprocable lengthwise of the liner, one sleeve being effective to obstruct variably the upstream ends of the ports and the other sleeve being effective to obstruct variably the downstream ends of the ports; and means for reciprocating the sleeves concurrently in the same direction to vary the effective location of the secondary air entrance means and for reciprocating the sleeves concurrently in opposite directions to vary the effective area of the secondary air entrance means, the lastnamed means including jointly reciprocable and jointly rotatable actuating rods coupled to the respective sleeves by reversely threaded screw and nut connections.

3. A combustion apparatus comprising a casing having an air inlet; a combustion liner of generally cylindrical configuration mounted in the casing, the liner having an upstream end and having a downstream end communicatingwith an outlet for combustion products, the liner defining primary air entrance means adjacent to the upstream end and secondary air entrance means intermediate the ends; and means adjacent to the upstream end for distributing fuel into the primary air; the said apparatus being characterized by variable swirl primary air entrance means and by variable configuration secondary air entrance means; the primary air entrance means comprising two sets of flow guides alternating around the liner, so that the guides define between them two sets of primary air inlet passages with the sets alternating and with the passages of one set directing the air with a different swirl component from the other set; and means for concurrently moving the guides of one set so as to vary relatively the areas of the passages of the two sets; the secondary air entrance means comprising a ring of ports through the liner; two valve sleeves reciprocable lengthwise of the liner, one sleeve being effective to obstruct variably the upstream ends of the ports and the other sleeve being effective to obstruct variably the downstream ends of the ports; and means for reciprocating the sleeves concurrently in the same direction to vary the effective location of the secondary air entrance means and for reciprocating the sleeves concurrently in opposite directions to vary the effective area of the secondary air entrance means. 

1. A combustion apparatus comprising a casing having an air inlet, a combustion liner of generally cylindrical configuration mounted in the casing, the liner having an upstream end and having a downstream end communicating with an outlet for combustion products, the liner defining primary air entrance means adjacent to the upstream end and secondary air entrance means intermediate the ends; and means adjacent to the upstream end for distributing fuel into the primary air; the said apparatus being characterized by variable configuration secondary air entrance means comprising a ring of ports through the liner; two valve sleeves reciprocable lengthwise of the liner, one sleeve being effective to obstruct variably the upstream ends of the ports and the other sleeve being effective to obstruct variably the downstream ends of the ports; and means for reciprocating the sleeves concurrently in the same direction to vary the effective location of the secondary air entrance means and for reciprocating the sleeves concurrently in opposite directions to vary the effective area of the secondary air entrance means.
 2. A combustion apparatus comprising a casing having an air inlet; a combustion liner of generally cylindrical configuration mounted in the casing, the liner having an upstream end and having a downstream end communicating with an outlet for combustion products, the liner defining primary air entrance means adjacent to the upstream end and secondary air entrance means intermediate the ends; and means adjacent to the upstream end for distributing fuel into the primary air; the said apparatus being characterized by variable configuration secondary air entrance means comprising a ring of ports through the liner; two valve sleeves reciprocable lengthwise of the liner, one sleeve being effective to obstruct variably the upstream ends of the ports and the other sleeve being effective to obstruct variably the downstream ends of the ports; and means for reciprocating the sleeves concurrently in the same direction to vary the effective location of the secondary air entrance means and for reciprocating the sleeves concurrently in opposite directions to vary the effective area of the secondary air entrance means, the last-named means including jointly reciprocable and jointly rotatable actuating rods coupled to the respective sleeves by reversely threaded screw and nut connections.
 3. A combustion apparatus comprising a casing haviNg an air inlet; a combustion liner of generally cylindrical configuration mounted in the casing, the liner having an upstream end and having a downstream end communicating with an outlet for combustion products, the liner defining primary air entrance means adjacent to the upstream end and secondary air entrance means intermediate the ends; and means adjacent to the upstream end for distributing fuel into the primary air; the said apparatus being characterized by variable swirl primary air entrance means and by variable configuration secondary air entrance means; the primary air entrance means comprising two sets of flow guides alternating around the liner, so that the guides define between them two sets of primary air inlet passages with the sets alternating and with the passages of one set directing the air with a different swirl component from the other set; and means for concurrently moving the guides of one set so as to vary relatively the areas of the passages of the two sets; the secondary air entrance means comprising a ring of ports through the liner; two valve sleeves reciprocable lengthwise of the liner, one sleeve being effective to obstruct variably the upstream ends of the ports and the other sleeve being effective to obstruct variably the downstream ends of the ports; and means for reciprocating the sleeves concurrently in the same direction to vary the effective location of the secondary air entrance means and for reciprocating the sleeves concurrently in opposite directions to vary the effective area of the secondary air entrance means. 